I have played most Pokemon games, but I am deciding between Pokemon Sun/Moon/Ultra and Brilliant Diamond.
I have never played either of these games not even their original versions. What do you think?
Additionally, is Sun/Moon good or is the Ultra version better?
I never finished Ultra, but the consensus I've heard is that normal SuMo has the better story, Ultra has the better postgame content and is at least somewhat more challenging. Which one is better really depends on what you're looking for in a Pokémon game.
I'm really liking ultra so far. There have been some challenging fight. But it is nothing that can't be overcome.
I did die to my first wild encounter though.